This document assumes that you have a working knowledge of Layers in Photoshop.

• Open your image file in Photoshop

• Make sure the Layers/Channels dialog is open and that your file is in RGB mode.

• Select the Channels tab and click on the New Channel button. It will automatically be given the name "alpha1".

• Make sure that the RGB channels are visible so that you can see what you are working on.

• Make the foreground color a shade of grey somewhere in between full white and full black. Whatever you draw in this color will modify the alpha value of each pixel drawn to be that color.

• Select the "alpha1" channel (and make sure all the RGB channels are unselected)

• Sample methods of drawing alpha masks
  • Using one of the selection tools (magic wand, lasso, etc) draw the shape of the area you wish to have the alpha which is your foreground color. Fill in the selected area using the bucket tool.

  • Use the paintbrush to paint an area with the alpha value.

  • Make the foreground color black. Select the Layer tab and select the layer containing your texture map image. Use the magic wand to select portions of the image to be made invisible. Go back to the Channels tab and select onlythe alpha channel. Paint the color black into the selected areas.

  • Select portions of an image from another layer or another image file. With only the alpha channel selected paste the selection.

• Save As a 32-bit targa file